Can the compressor impeller for MVR evaporation of NaCl brine be made of stainless steel or duplex steel?
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We use MVR to evaporate NaCl brine. The steam containing secondary condensate (with a TDS of generally less than 50 ppm) is fed into the MVR compressor. Some manufacturers claim that the impeller must be made of titanium, while others say that duplex steel can be used as an alternative; titanium offers better corrosion resistance but at a higher cost； If dual-phase steel is chosen, the price is lower, but I’m not sure if it can operate over the long term?
Dual-phase steel can be used; generally, its tolerance to chloride ions is 20,000 mg/l, which is equivalent to 2%. Therefore, impellers used for compression will not have any problems, and even if contamination occurs, it remains relatively safe
It should be determined based on the chloride content in the medium; generally, duplex steel meets the requirements fully.
Both molybdenum-containing austenitic stainless steels and duplex stainless steels are suitable; it is crucial to clean the secondary steam with saturated water before it enters the compressor.
Is a forced circulation pump necessary? We encounter this situation quite often; in most cases, we manufacture pumps made of 2205 material for our customers, while a smaller number of customers opt for titanium. In fact, titanium is not as expensive as people think. The pumps we produce from Ta2 alloy are available at very low prices
When selecting materials for compressor impellers, corrosion resistance is not the only factor to consider. Theoretically, 2205 should be sufficient; if a fan design is used, its strength meets the requirements as well. However, with a compressor design, the rotation speed is too high, and the strength of 2205 is not adequate in such cases – TC4 or TC11 must be used instead
If you can ensure that the droplets do not come out along with the secondary steam, duplex steel is sufficient; if this cannot be guaranteed, then for the sake of system stability, it is recommended to use titanium. It costs only a little more – 136--5095--7236 for more details
I am from Shandong Sanniu Machinery Co., Ltd., where we independently develop, manufacture, sell, and provide service for Roots steam compressors and Roots blowers. I will do my best to help resolve any issues related to steam compressors. 132-5666-5060
I work with rotary compressors. For the evaporation of sodium chloride solutions, rotary compressors of type 2205 are suitable; their lower speed is sufficient. The strength of these compressors is adequate, and they can also resist chloride corrosion. Corrosion becomes more severe when the machines are shut down for long periods of time
If you’re still worried, you can perform vapor-liquid separation once more before air enters the compressor! Separator stage 1: Wire mesh demister ； Vapor-liquid separation tank, once ； Two separations ensure no droplets are entrained!